Proteases (also called Proteolytic Enzymes, Peptidases, or Proteinases) are enzymes that hydrolyze the amide bonds within proteins or peptides. Most proteases act in a specific manner, hydrolyzing bonds at or adjacent to specific residues or a specific sequence of residues contained within the substrate protein or peptide. Proteases play an important role in most diseases and biological processes including prenatal and postnatal development, reproduction, signal transduction, the immune response, various autoimmune and degenerative diseases, and cancer. They are also an important research tool, frequently used in the analysis and production of proteins. Furin is a calcium dependent serine endoprotease that processes numerous proproteins of different secretory pathways into their mature forms by cleaving at the carboxyl side of the recognition sequence, R-Xaa-(K/R)-R, where Xaa can be any amino acid. Recombinant human Furin is a 61.7 kDa protein, corresponding to residues 124 through 715 of the Furin precursor plus a C-terminal His tag.